# -ve square wave using a dc voltage

1. ## -ve square wave using a dc voltage

Hi,

Is it possible to get a square wave with both 40v +ve & 40v -ve sides, using a 40vdc and a 5v squarewave ?

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2. ## Re: -ve square wave using a dc voltage

Hi,

There is a lot of information missing.
A picture could help.

Your question is: "is it possible.."
My anser is: YES.

using a 40vdc and a 5v squarewave ?
I assume you mean a sinlge 40V DC power supply (0V, +40V)
--> use a DPDT relay with 5V coil voltage:
* one NC1 to 40V, the NO1 from the same contact to 0V
* other contact NO2 to 40V, NC2 to 0V
* coil connected to GND and 5V square wave.
* output: COM1 and COM2

Connect a scope or DVM to COM1 abd COM2 and see +/-40 square wave.
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Similar solutions can be made using an DPDT analog switch (faster, low power)
Or with a MOSFET power full bridge (fast, high power)
...and maybe hundreds of other solutions....depending on your (missing) specifications.

Klaus

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3. ## Re: -ve square wave using a dc voltage

I want to test this circuit but I have only 40volt supply.
I need both positive and negative voltage at the output.

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4. ## Re: -ve square wave using a dc voltage

Hi,

If you need both positve and negative output you need both positve and negative supply.

But I doubt the 741 is specified to work with +/- 40V supply.

* I wonder why you talk about 5V square wave... This has nothing to do with the shown circuit.

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Please give complete and detailed informations .. not piece by piece.

Klaus

5. ## Re: -ve square wave using a dc voltage

Not sure exactly what you need, but you can create a negative rail from a positive DC supply. See this video https://youtu.be/LtoPHevexTM

6. ## Re: -ve square wave using a dc voltage

The video in post #5 is informative. It discusses a charge pump. The same concept is used in this simulation, where you get -38V by drawing power from a +40V supply.

For the clock signal, you can make that your 5V square wave. It can drive a low side NPN. Then add another NPN in such a way as to drive the high side PNP on/ off.

If you were to decide that a bipolar +-20V supply is suitable, then it would be convenient and efficient to split your +40V supply.

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7. ## Re: -ve square wave using a dc voltage

sure, use a transformer with the output center tapped. connect 40V to center tap, and put 5V square wave on primary

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